下穿高速公路的浅埋大跨隧道开挖力学行为分析

Analysis of the Mechanical Behaviors of Shallow-Buried Large-Span Tunnels under Expressways

深圳市红棉路隧道具有埋深浅(约6 m)、跨度大(16 m左右)、周围围岩软弱、下穿机荷高速公路的距离长等特点。由于机荷高速公路车流量非常大、动态荷载强,因此该隧道施工难度高、风险极大。为研究该隧道开挖过程的力学行为,文章通过数值计算及现场测试方法,获得了隧道下穿高速公路施工过程中地表沉降、隧道拱顶沉降、掌子面挤出位移,初期支护钢拱架应力以及二次衬砌应力的动态变化规律。研究结果表明,在隧道开挖过程中,掌子面前方先行变形的影响范围为1~1.5倍洞跨。隧道掌子面进行锚喷支护加固措施,对减小隧道掌子面的挤出位移作用效果明显。同时,需合理确定支护时机,适当优化施工工序,加快隧道断面闭合时间,加强监控量测,确保隧道成功穿越机荷高速公路。

The construction of the Hongmianlu Tunnel in soft rock is difficult and high risk due to its shallow bur- ied depth （about 6 m）, large span（about 16 m） and long distance under the Jihe Expressway, which has a large traffic volume and strong dynamic load. To study mechanical behaviors during tunnel excavation, the dynamic variation laws of ground settlement, crown settlement, extrusion displacement of the tunnel face, steel arch stress in the prima- ry support and the stress in the secondary lining were obtained by numerical calculations and field tests. The results show that the influential scope of the antecedent deformation is 1-1.5 times the tunnel span. By anchoring and shot- creting at the tunnel face, the extrusion displacement of the tunnel face decreases significantly. To guarantee suc- cessful construction under the Jibe expressway, it is necessary to determine a reasonable support time, optimize the construction procedure, decrease the closure time of the tunnel section and improve site monitoring.